Collaborative Research: Reconciling conflicting Arctic temperature and fire reconstructions using multi-proxy records from lake sediments north of the Brooks Range, Alaska

合作研究：使用阿拉斯加布鲁克斯山脉以北湖泊沉积物的多代理记录来协调相互矛盾的北极温度和火灾重建

• 批准号: 1503846
• 负责人: Yongsong Huang
• 金额: $ 55.62万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-15 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1503846&HistoricalAwards=false
• 关键词: Collaborative; Research; Reconciling; conflicting; Arctic

Temperature reconstructions from the region north of the Brooks Range in Alaska suggest a warmer-than-present Last Glacial Maximum (LGM, 26,500 to 19,000 years ago). Global climate models differ strongly in their simulations of this region, with some suggesting a warmer and others a colder cliamte. There are virtually no high-resolution temperature records from this region. Robust temperature reconstructions spanning the LGM to present are therefore needed to test the outputs from climate models and to understand regional sensitivity to climate forcing. Associated with the ambiguous temperature history is uncertainty in the regional fire history, as revealed by the unexpected discovery of three major Alaskan tundra fires in last 150 years. These fires contradict the conventional notion that tundra ecosystems rarely, if ever, burn and stimulate a key question: What are the relationships between climate change, fire, and vegetation since the LGM? This project will develop careful reconstructions of temperatures in the region using records obtained from lake cores. The resulting data will then be compared with a variety of climate model outputs.The project will contribute to workforce development by supporting the training of two graduate students. The students and their mentors will leverage activities of the Brown STEM Outreach Office to K-12 classrooms in Providence, RI, where the classroom population is composed largely of under-represented minorities in the STEM fields. The project will entrain a K-12 teacher into the laboratory during the summer and support the teacher's participation in a major regional science meeting. The team will participate in the Kaktovik Oceanography Program, a project in the Inupiat village of Kaktovik, Alaska for K-12 students. The data collected will be made public and serve as a reference for Alaskan tundra science. Finally, the principal investigators will expand an existing project blog into a dedicated website for public outreach concerning the project.The PIs will generate high resolution, multiproxy records of temperature and fire since the LGM from sediment cores of four lakes on the North Slope of Alaska using a suite of organic geochemical and traditional paleoecological proxies. These data will be tested against predictions from fully coupled climate models to evaluate the ability of IPCC-grade models to simulate past temperature changes, and to evaluate potential forcings and feedbacks that regulate regional temperatures. The work is built upon initial studies that indicate that: 1) strong, quantifiable relationships exist between alkenone distributions and early summer temperature in these lakes, and plant leaf wax D/H ratios in Arctic lake sediments record mean summer temperatures; 2) polycyclic aromatic hydrocarbons (PAH) in lake sediments record the regional fire history; and 3) multiproxy analysis can determine temperature changes in early, middle and mean summer temperatures and will permit critical examination on the impacts of seasonal temperature change and its associated feedbacks and forcing. The PAH approach complements charcoal records and allows detection of paleo-fires across a broader regional scale. Study sites are located within the Toolik Field Station Arctic Long Term Ecological Research (LTER) site, which only began to provide continuous, strategically important monitoring data since 1975. The study will provide fundamental, high quality temperature and fire data, placing the past 40 years of instrumental monitoring in the grand context of the Holocene and late Pleistocene.

阿拉斯加布鲁克斯山脉以北地区的温度重建表明末次盛冰期（LGM，距今 26,500 至 19,000 年前）比现在温暖。全球气候模型对该地区的模拟差异很大，一些模型认为气候变暖，另一些则认为气候寒冷。该地区实际上没有高分辨率的温度记录。因此，需要对末次盛冰期至今的稳健温度重建进行测试，以测试气候模型的输出并了解区域对气候强迫的敏感性。与模糊的温度历史相关的是区域火灾历史的不确定性，正如过去 150 年来意外发现的三场阿拉斯加苔原大火所揭示的那样。这些火灾与苔原生态系统很少（如果有的话）很少燃烧的传统观念相矛盾，并引发了一个关键问题：自末次盛冰期以来，气候变化、火灾和植被之间的关系是什么？ 该项目将利用从湖芯获得的记录对该地区的温度进行仔细的重建。然后将所得数据与各种气候模型输出进行比较。该项目将通过支持两名研究生的培训来促进劳动力发展。 学生和他们的导师将利用布朗 STEM 外展办公室的活动，在罗德岛州普罗维登斯的 K-12 教室开展活动，那里的教室人口主要由 STEM 领域代表性不足的少数族裔组成。 该项目将在夏季邀请一名 K-12 教师进入实验室，并支持该教师参加主要的区域科学会议。 该团队将参加卡克托维克海洋学计划，这是一个在阿拉斯加卡克托维克因努皮特村为 K-12 学生举办的项目。收集到的数据将公开并作为阿拉斯加苔原科学的参考。 最后，主要研究人员将把现有的项目博客扩展为一个专门的网站，用于与该项目相关的公众宣传。PI 将从阿拉斯加北坡四个湖泊的沉积物核心中生成自末次盛冰期以来的温度和火灾的高分辨率、多代理记录使用一套有机地球化学和传统古生态代理。这些数据将根据完全耦合气候模型的预测进行测试，以评估 IPCC 级模型模拟过去温度变化的能力，并评估调节区域温度的潜在强迫和反馈。这项工作建立在初步研究的基础上，这些研究表明：1）这些湖泊中的烯酮分布和初夏温度之间存在很强的、可量化的关系，北极湖泊沉积物中的植物叶蜡 D/H 比率记录了夏季平均温度； 2）湖泊沉积物中的多环芳烃（PAH）记录了区域火灾历史； 3）多代理分析可以确定夏季初、中和平均气温的变化，并允许对季节性温度变化及其相关反馈和强迫的影响进行严格检查。 PAH 方法补充了木炭记录，并允许在更广泛的区域范围内检测古火灾。研究地点位于 Toolik 野外站北极长期生态研究 (LTER) 站点内，该站点自 1975 年才开始提供连续的、具有战略意义的重要监测数据。该研究将提供基本的、高质量的温度和火灾数据，将过去 40在全新世和晚更新世的大背景下进行了多年的仪器监测。